Cylindrical elongated furnace for treating material at high temperature in a gaseous atmosphere under high pressure

ABSTRACT

A cylindrical elongated furnace for treating material at high temperature in a gaseous atmosphere under high pressure is formed of a high pressure cylinder with end closures projecting into it and a furnace chamber arranged in the high pressure cylinder. The furnace chamber is insulated from the walls of the pressure chamber by a cylindrical casing having gas-impermeable tubes arranged one inside the other with an insulation between them. At least one layer of insulating material in the casing engages only the outer or inner surface of one tube and is spaced from the adjoining tube, the space between being filled with gas. The insulating material may be held against the outside of one of the tubes by rings or a spiral strip running helically.

United. States Patent [191 Larker et al. Feb. 5, 1974 CYLINDRICAL ELONGATED FURNACE 3,185,460 5/1965 Mescher et al. 432/249 x FOR TREATING MATERIAL AT HIGH 3,598,378 8/1971 Lund strom TEMPERATURE IN A GASEOUS 3,743,132 7/1973 Larker 432/250 ATMOSPHERE UNDER HIGH PRESSURE [75] Inventors: Hans Larker; Sven-Erik Isaksson; Primary Examiner-John Camby Mats Lindberg, all of Robertsfors; Gunnar Granberg, Umea, all of 1 Sweden 57 ABSTRACT [73] Assignee: Allmanna Svenska Elekriska Aktiebolaget, Vasteras, Sweden A cylindrical elongated furnace for treating material at hi h tem erature in a aseous atmos here under [22] Flled: June 1973 high pressur is formed 0% a high presssre cylinder [21] Appl. N0.: 367,101 with end closures projecting into it and a furnace chamber arranged in the high pressure cylinder. The furnace chamber is insulated from the walls of the [30] Forelgn Apphcanon Pnomy Data pressure chamber by a cylindrical casing having gas- June 13, Sweden.., impermeable tubes arranged one inside the other D80. 29, 1972 Sweden..' 17130/72 a insulati n between them At least one layer of insu. lating material in the casing. engages only the outer or US. Cl. inner surface of one tube and is Spaced from the ad- Int- Cl. n joining tube the pace between being gas [58] Field of Search 432/247, 249, 251, 252 The insulating material may be held against the side of one of the tubes by rings or a spiral strip run- [56] References Cited ning 1 11 UNITED STATES PATENTS 1 2,421,148 6/1947 10 Claims, 5 Drawing Figures Crocker 432/249 X PATENTEDFEB 5 1974 3.790.339

sum 1 or 3 6| Fig] PATENTEDFEB 5M4 3790.339

SHEET 2 [IF 3 PAIENTEDFEB 5197+ I 3.790.339

sumsurs CYLINDRICAL ELONGATED FURNACE FOR TREATING MATERIAL AT HIGH TEMPERATURE IN A GASEOUS ATMOSPHERE UNDER HIGH PRESSURE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical elongated, preferably vertical furnace for simultaneous treatment of material at high temperatures, up to 1,500C, in a gaseous atmosphere under high pressure, preferably 500 bar and above.

2. The Prior Art The problems involved with furnaces of this type, as well as such a furnace, have been described in U.S. Pat. Nos. 3,598,378 and 3,628,779.

In high pressure furnaces the furnace chamber must be insulated from the walls of a pressure chamber since these must be kept below a certain temperature to avoid unduly affecting their strength and since the heat losses must be kept down in order to be able to reach the desired temperature at all with a reasonable supply of power. The thickness of the insulation must also be kept down since the pressure chamber space is expensive and the cost of the pressure chamber increases sharply with increased diameter. The insulation is therefore an extremely important part in a pressure furnace.

Furnace insulation arrangements having a cylindrical insulating casing, usually constructed of a number of tubes arranged one inside the other with insulation in the gaps between the tubes, have been found to give extremely good insulation and the thickness of the casing can therefore be kept slight. However, it has been found that the tubes may buckle because they are sujected to too great axial forces, the outermost tube particularly being subjected to such forces. These .forces when the insulating casing is cooling, since the inner tubes which have been heated to high temperatures shrink more than the outer tubes when cooling. Because of friction betweenthe insulation in the outermost annular gap and the outermost tube, the outermost tube is subjected to impermissibly high axial pressure stresses and may buckle. This has led to damage to the insulation during the next heating process and also to causing the tube to come into contact with the wall of the pressure chamber, thus making replacement of the insulating sheath more difficult. In the worst case, the insulating sheath is impossible to remove without being completely destroyed.

SUMMARY OF THE INVENTION The present invention eliminates the drawbacks mentioned. The furnace according to the invention comprises a cylindrical pressure chamber consisting of a high pressure cylinder with end closures projecting into it, pressure-absorbing members which take up the axial forces exerted on the end closures, and a furnace chamber arranged in the pressure chamber and insulated from the walls of the pressure chamber by a cylindrical casing having gas-impermeable tubes arranged one inside the other with insulation arranged between them, an insulating lid and an insulating bottom. It is substantially characterisedin that there is at least one layer of insulating material in the casing, one side of said insulating material abutting the outer or inner surface of a tube and the other side facing a space filled with gas. The tubes are generally made of sheet-metal tubing and the insulating material is a fibrous material. This is kept pressed against one side of a tube by strips or clamp rings which may be arranged helically in or around the insulating material. The rings or strips may be resilient. It is also possible to glue a layer of insulating material in or on the tube. At the high temperatures occurring in furnaces of this type, it may be necessary in certain cases to use ceramic substances as the adhesive material. A layer of insulating material may be placed both internally and externally on a tube.

The insulating material may be a felt-like material and the insulating layer may consist of one or more layers of an insulating blanket which is wrapped around a tube or applied inside a tube.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further described with reference to the accompanying drawings.

FIG. 1 shows a pressure furnace; FIG. 2 shows,on a larger scale, an insulating casing in the furnace in the area indicated at A-A in FIG. 1'; FIG. 3 shows a detail of this casing; FIG. 4 is a casing of alternative design; and FIG. 5 a detail of the casing of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, 1 designates a press stand which is arranged to be movable between the position shown in FIG. 1 and a position where it surrounds the pressure chamber 2. The press stand is of the, type consisting of yokes 3 and 4, intermediate spacers 5 and a prestressed strip casing 6 holding it together. The stand is carried by wheels 7 running on rails 8. The high pressure chamber 2 is supported by a pillar 9. It comprises a high pressure cylinder 10 constituted by an inner tube 11, a surrounding, pre-stressed strip casing 12 and end rings 13 which hold the strip casing together axially and provide attachments forbrackets 14 by means of which the chamber is attached to the pillar '9. The chamber has an upperend closure 15 which projects into the tube 11 of the high pressure chamber. Between the tube and the end closure is a sealing ring 16. The furnace chamber 17, in which the charge 18 is inserted, is surrounded by an insulating casing 19 which is suspended in the upper end closure 15 and gas-tightly connected to it. In theupper part of the casing 19 is an insulating lid 21 which is connected by an attachment ring 22 to the attachment ring 23 of the casing 19. In the upper end closure is a gas channel 24for the supply of pressure medium and a lead-in 25 for an electric cable 26. The channel 24 opens into the gap 27 between the tube 10 and the sheath 19. In the furnace chamber 17 are heating elements 28 supported by a tube 30. Above the upper end closure is a pressure plate 31 with a groove for the electric cable 26. The pressure chamber has a lower end closure consisting of an annular part 32 permanently arranged in the cylinder l0 and a bottom 33 projecting into the cylinder with an insulating bottom 34. Between the tube 10 and the part 32 and between the part 32 and the bottom 33 are seals 35 and 36. The bottom '33 is attached by a bracket 37 to a sleeve 38 running along a guide 40 which is attached to the pillar 9. The bottom 33 can be raised and lowered by an operating cylinder 41, the piston rod 42 of which is attached to the bracket 43 on the sleeve 38.

As shown in FIG. 2, the casing 19 comprises three concentric tubes 44, 45 and 46, all of which are suspended from the attachment ring 23. The tube 45 is firmly attached at its lower end to thering 47, whereas the tubes 44 and 46 can move freely in relation to ring 47 as they expand or contract to different lengths when heated or cooled. The space between the tubes 44 and 45 is filled with insulating material 48 which will stand high temperatures. Outside the tube 45 is a layer 50 of insulating material, one side of which lies only or substantially only against the tube 45 and the other side of which faces the gap 53 between the layer of insulating material 50 and the tube 46. This is kept in place by a helically wound, slightly resilient strip 51. The compression of the insulating layer effected by the strip has a dampening effect on the ,vertical gas circulation through the insulating layer. The insulating layer 50 may consist of a felt material sold under the name Fiberfrax," or of a felt material constructed of carbon fibers. The tube 45 may be made of stainless steel, molybdenum or in an alloy sold under the name l-Iastaloy X." It is feasible to use ceramic tubes onto which an insulating material has been glued or graphite tubes onto which carbon felt has been secured with carbon fibers. The resilient strips are also preferably made of the materials mentioned. For a felt thickness of 12 mm which, after application, is compressed to 6 8 mm in thickness, l mm is a suitable spacing between the turns of the strip 51. For a satisfactory result the spacing between the clamping-elements must be less than 10 times, preferably less than 5 times, the thickness of the insulating layer compressed by these elements. As seen in FIGS. 2 and 3, there is' normally a clearance between the felt layer 50 and the tube 46 so that the friction between this layer and the tube is eliminated, thus also eliminating the stresses in the tube 46 caused by varying lengths of the tubes 45 and 46.

FIG. 3 shows how with a sheet-metal ring 52, which is secured at the upper end to the wall 45 and has an outward projection at its lower end extending partly through the width of the layer 48, the vertical gas circulation in the gap between the tubes 44 and 45 can easily be reduced if there is any damage to the insulating layer 48.

In FIGS. 4 and 5, 60 designates an insulating casing which is intended to be suspended from the upper end closure of a pressure chamber. the casing comprises three concentric sheet-metal tubes which are secured at the top in an attachment ring 64. The outer tube 63 has a lower guide ring 65. The inner tube 61 is guided by the opening 66 and the tube 62 by the groove 67 in the ring 65. Between the tubes 61 and 62 is a layer of extremely heat-resistant insulating material 68. Outside the tube 62 is a layer ofa porous insulating material 69 comprising one or more layers of a web of fibrous material. This is kept pressed against the sheet-metal tube 62 by a number of rings or a helically wound strip 70. The tube 63 is provided with insulating layers 71, 72 both on the inside and the outside. These layers are pressed against the tube by rings or strips 73 and 74, respectively. One side of the insulating layers 68 and 71 faces the gap 75 between the layers. One side of the insulating layer 72 faces a space filled with gas between the insulating layer around the tube 1 1 of the surrounding pressure chamber '10.

- We claim:

1. Cylindrical elongated furnace for treating material at high temperature in a gaseous atmosphere under high pressure, including a cylindrical pressure chamber comprising a high pressure cylinder with end closures projecting into it, pressure-absorbing members which take up the axial forces exerted on the end closures, a furnace chamber arranged in the high pressure chamber, means insulating the furnace chamber from the walls of the pressure chamber comprising a cylindrical casing having gas-impermeable tubes arranged one inside the other with insulation arranged between them, an insulating lid and an insulating bottom, in which there is at least one layer of insulating material in the casing, one side of said insulating material abutting one of the outer and inner surfaces of a tube and the other side facing a space filled with gas.

2. Furnace according to claim 1, in which the tube is a metal tube.

3. Furnace according to claim 1, in which the insulating material is a fibrous material.

4. Furnace according to claim 1, in which means are provided for pressing the insulating material against the tube comprising at least one elongated member extending around the insulating material.

5. Furnace according to claim 4, in which such elongated member is arranged helically.

6. Furnace according to claim 4, in which the pressing means extends around the insulating material at least twice and the spacing of the pressing means is less than 5 times the thickness of the pressed thereby.

7. Furnace according to claim 4, in which the pressing means is resilient.

8. Furnace according to claim 1, in which the insulating material is glued to the tube.

9. Furnace according to claim 1, in which the insulating casing includes three tubes arranged one inside the other, the insulating material including a layer of insulating material abutting only'the central tube.

10. Furnace according to claim 9, in which the outer tube has a layer of insulating material on one of its faces abutting only theouter tube. t t l l insulating layer com- Disclaimer 3,790,339.Hms Larker, Sven-Erik I saicsson, and Mats Lindberg, Robertsfors,

and Gun mar Grcmberg, Umea, Sweden. CYLINDRICAL ELON- GATED FURNACE FOR TREATING MATERIAL AT HIGH TEMPERATURE IN A GASEOUS ATMOSPHERE UNDER HIGH PRESSURE. Patent dated Feb. 5, 1974. Disclaimer filed Nov. 24, 1975, by the assignee, Allmomna Seems/ca Elekzfrz'slca Aktz'ebolaget. Hereby enters this disclaimer to claims 1, 2, 3, 8 and 9 of said patent.

[Oficial Gazette February 10, 1.976.] 

1. Cylindrical elongated furnace for treating material at high temperature in a gaseous atmosphere under high pressure, including a cylindrical pressure chamber comprising a high pressure cylinder with end closures projecting into it, pressureabsorbing members which take up the axial forces exerted on the end closures, a furnace chamber arranged in the high pressure chamber, means insulating the furnace chamber from the walls of the pressure chamber comprising a Cylindrical casing having gasimpermeable tubes arranged one inside the other with insulation arranged between them, an insulating lid and an insulating bottom, in which there is at least one layer of insulating material in the casing, one side of said insulating material abutting one of the outer and inner surfaces of a tube and the other side facing a space filled with gas.
 2. Furnace according to claim 1, in which the tube is a metal tube.
 3. Furnace according to claim 1, in which the insulating material is a fibrous material.
 4. Furnace according to claim 1, in which means are provided for pressing the insulating material against the tube comprising at least one elongated member extending around the insulating material.
 5. Furnace according to claim 4, in which such elongated member is arranged helically.
 6. Furnace according to claim 4, in which the pressing means extends around the insulating material at least twice and the spacing of the pressing means is less than 5 times the thickness of the insulating layer compressed thereby.
 7. Furnace according to claim 4, in which the pressing means is resilient.
 8. Furnace according to claim 1, in which the insulating material is glued to the tube.
 9. Furnace according to claim 1, in which the insulating casing includes three tubes arranged one inside the other, the insulating material including a layer of insulating material abutting only the central tube.
 10. Furnace according to claim 9, in which the outer tube has a layer of insulating material on one of its faces abutting only the outer tube. 